ID | Technique | Tactic |
---|---|---|
T1098 | Account Manipulation | Persistence |
T1098.002 | Additional Email Delegate Permissions | Privilege Escalation |
Detection: O365 Mailbox Folder Read Permission Assigned
Description
The following analytic identifies instances where read permissions are assigned to mailbox folders within an Office 365 environment. It leverages the o365_management_activity
data source, specifically monitoring the ModifyFolderPermissions
and AddFolderPermissions
operations, while excluding Calendar, Contacts, and PersonMetadata objects. This activity is significant as unauthorized read permissions can lead to data exposure and potential information leakage. If confirmed malicious, an attacker could gain unauthorized access to sensitive emails, leading to data breaches and compromising the confidentiality of organizational communications.
Search
1`o365_management_activity` Workload=Exchange (Operation=ModifyFolderPermissions OR Operation=AddFolderPermissions) Workload=Exchange object!=Calendar object!=Contacts object!=PersonMetadata
2| eval isReadRole=if(match('Item.ParentFolder.MemberRights', "(ReadAny)"), "true", "false")
3| rename UserId as user
4| stats count earliest(_time) as firstTime latest(_time) as lastTime by Operation, user, object, Item.ParentFolder.MemberUpn, Item.ParentFolder.MemberRights
5| `security_content_ctime(firstTime)`
6| `security_content_ctime(lastTime)`
7| `o365_mailbox_folder_read_permission_assigned_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
N/A | N/A | N/A | N/A | N/A |
Macros Used
Name | Value |
---|---|
o365_management_activity | sourcetype=o365:management:activity |
o365_mailbox_folder_read_permission_assigned_filter | search * |
o365_mailbox_folder_read_permission_assigned_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
Known False Positives
Mailbox folder permissions may be configured for legitimate purposes, filter as needed.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
A folder was granted read permission by $user$ | 42 | 70 | 60 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | o365 |
o365:management:activity |
Integration | ✅ Passing | Dataset | o365 |
o365:management:activity |
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
Source: GitHub | Version: 2